valve spring swap -- need help

[Old Guy with 87 GT]

i'm planning on swapping my valve springs tommorow ......i'm going to do it with the heads on the car(friend of mine has tools ,using air )....i'm replacing stock springs with crane kit 44-308-1

well i'm planning on having a friend help me thats a little bit more knowlegable then me......but this is new territory for me ,i've never done this myself and i want to make sure i do it right ......i'm not a total novice but i still have alot to learn

what do i need to know before i start this job .......i was told i will have to check spring height and pressure ....i might have to use washers to shime spring height .....not sure the proper way to do this so any help or advice would be greatly appriciated

if there's any other thing i should know ....please tell me i don't want to do this again

details>its on the 87gt ,i'm using stock valves on milled 7ete heads(.02) with 1.7 rollers ...it was recommende to use the crane kit i got ,(44-308-1)should have sufficient pressure....the heads were just reconditioned with all the clearances checked and i'm going to pessurize the cylinders to hold the valves in place

thanks in advance for any replys